KöMaL 2006 B3947

Let $h$ denote the length of the tangents drawn to a circle from an exterior point $P$, and let the midpoint of the line segment connecting the points of contact be $F$. Prove that a chord $AB$ of the circle satisfies the equality $AP^. PB$=$h^2$ if and only if the line $AB$passes through the point $P$ or the point $F$.